Inhibited single-phase anti-freeze formulations and method



United States Patent 3,282,846 INHIBITED SINGLE-PHASE ANTI-FREEZE FORMULATIONS AND METHOD William P. Scott, Pouca City, Okla., assignor to Continental Oil Company, Ponca City, Okla, a corporation of This invention relates to anti-freeze formulations for use in the circulating cooling system of an internal combustion engine or like device. More particularly, the invention relates to polyhydric alcohol anti-freeze formulations which are inhibited against corrosion, which have antiseep properties, and which are single phase or a homogeneous system and an advantageous method of blending said formulations.

This application is a continuation of my copending application Serial No. 12,914, filed on March 7, 1960, now abandoned, having the same title.

The prior anti-freeze compositions, both the permanent and nonpermanent type, cause serious corrosion of metals in admixture with water as they are normally employed. Attempts to remedy this situation have been made, With only partial and very limited success, that is, of the metals steel, brass, copper, aluminum, solder, and cast iron which are all normally in cooling systems of internal combustion engines, at least one and usually more than one still suffer from substantial corrosion. Some of the prior art anti-freeze compositions are multiphased as a result of the various components added to obviate the more serious disadvantages. These and even prior art single-phase anti-freeze compositions experience difficulty in keeping the valuable additives in solution which complicates handling and often results in their being lost by the average purchaser of the consuming public. The two-phase antiwv freeze formulations suffer the additional disadvantage over single phase formulations heretofore of usually possessing an oil phase, and the oil of such a system interferes with proper heat transfer in an operating engine. Many anti-freeze compositions further are lost or partially lost from the cooling system by seepage through capillary fissures, pin holes, or cracks in the cooling system.

It is therefore a principal object of this invention to provide a single-phase anti-freeze composition which is in comparison to prior art, substantially noncorrosive to the structional metals of cooling systems.

It is another object to provide an anti-freeze formulation having the above properties and, in addition thereto, a reduced tendency to seep from cooling systems.

It is still another object to provide an advantageous and superior method for blending the above compositions.

Other objects are to eliminate or substantially lessen and reduce the disadvantages of prior art anti-freeze formulations.

The foregoing and other related ends are accomplished by the present invention which is in one aspect an antifreeze additive composition comprising sodium borate and sodium metasilicate. In another aspect, the invention is an anti-freeze concentrate comprising ethylene glycol, water, sodium borate, and sodium metasilicate.

Another and preferred embodiment of the invention is a composition comprising ethylene glycol, water, sodium borate, sodium metasilicate, and sodium mercaptobenzothiazole.

Still another preferred embodiment is a composition or formulation comprising ethylene glycol, water sodium borate, sodium metasilicate, and sodium mercaptobenzothiazole.

3,282,846 Patented Nov. 1, 1966 Still another preferred embodiment is a composition or formulation comprising ethylene glycol, water sodium borate, sodium metasilicate, sodium mercaptobenzothiazole, and a noncorrosive and miscible organic phosphate, such as and preferably, tributoxyethylphosphate.

It has been found in this invention that the particular components especially when employed in the hereinafter to be specified quantities exhibit snyergism.

Of course, the inhibitor compositions of this invention are for use with water miscible high boiling polyhydroxy alcohols and are not necessarily restricted to ethylene glycol. Ethylene glycol, however, is the most preferred anti-freeze; but glycerine and other glycols, such as propylene glycol, diethylene glycol, and mixtures thereof, are also suitable.

With regard to the phosphorus compounds, the preferred is indicated as tributoxyethylphosphate; however suitable organic compounds have the general formula:

wherein R is hydrogen, alkyl or a substituted alkyl group, R is an alkyl or a substituted alkyl group, alkoxy or substituted alkoxy, x is an integer varying from 0 to 2, and y equals 2-x. As to the solubility requirements, the organic phosphorus compound must have a minimum solubility in ethylene glycol of .25 weight percent and a minimum solubility in a 40 percent aqueous ethylene glycol solution of .042 percent.

Additional teachings with respect to these phosphorus compounds may be found in a copending case wherein applicant is co-inventor having the Serial No. 797,828, filed March 9, 1959, now US. Patent No. 3,042,620, and any and all teachings of said application are made a part of this disclosure.

While various embodiments of the present invention in the form of the combination of components, as well as the quantities, are operable due to the wide difference in result had between these embodiments, they are not necessarily equivalents and are thus not to be considered as such.

The broad and preferred quantities of the components in parts by weight are set forth for convenience in tabular form as follows:

It is thus seen that the broad range of glycol possible in each of the varying embodiments of the antifreeze formulation are as follows:

96.99 to 91.70 Where the composition contains sodium tetraborate pentahydrate, sodium metasilicate pentahydrate, and water in addition to the glycol.

96.985 to 91.20 where the composition contains sodium tetraborate pentahydrate, sodium metasilicate pentahydrate, sodium mercaptobenzothiazole, and water in addition to the glycol.

96.975 to 89.20 where the composition contains sodium tetraborate pentahydrate, sodium metasilicate pentahydrate, sodium mercaptobenzothiazole, tributoxyethylphosphate, and water in addition to the glycol.

In the above tabulation of broad and preferred ranges of components, it is to be understood that the exact ranges given relate to the exact form of the compounds employed; but the particular form of the compound in the table is illustrative and not limiting. For example, sodium tetraborate pentahydrate is given in particular ranges in the table. However this does not limit the invention to the pentahydrate, as the compound may be used in, for example, the decahydrate form; but the quantities would be different. Equivalent quantities of the decahydrate would be applicable, which can be readily determined by those skilled in the art. It is also to be understood that the total water from all sources includes the water of both dilution and hydration. It is to be further understood that the sodium mercaptobenzothiazole can be prepared in situ from sodium hydroxide and mercaptobenzothiazole. It is to be pointed out that, as is well known, any quantity of the glycol is operable; however the effect in lowering the freezing point of the waterm the cooling system is one of degree varying directly with the quantity of glycol and thus is to be kept at a maximum in the composition.

Of course, it goes without saying that the compositions discussed throughout this disclosure are the concentrate and that in practice they are added to water in a cooling system in a quantity sufiicient to lower the freezing point of the final solution to the desired temperature. Therefore, there actually is no limitation on the amount of water which the composition may contain, and there is no minimum on how much glycol must be used in order that it function efiectively ultimately in use.

As mentioned hereinafter however, packaging limitations with regard to volume can require adjustments in the amounts of one or more components in the formulations in order to satisfy such packaging requirements, and it has been stated that the glycol content of the formulation is to be kept at a maximum which has been indicated herein also as about 95 parts per 100 parts and thus the upper portion of the broad ranges of inhibitor systems is rarely if ever employed. The length and particular conditions of service can vary the amount of the corrosion inhibitor system and thus the amount to be employed is difiicult to predict for all cases but an effective or corrosion inhibiting amount is to be employed, which amount can be readily determined by routine testing following the teachings here and/ or other test methods known in the art.

The data given hereinafter in Tables I and II show the synergism and superiority of the present formulations, especially with regard to corrosion in a cooling system. Included for comparison are results obtained with several different commercially marketed anti-freezes. These are indicated here by Brands A, B, and C. The table clearly shows these to be more corosive when employed in a cooling system than the formulations of the present invention.

In the first column of the tables, the components and quantity of each are given, the latter in parts by weight as indicated therein. In addition to the components given in the specific examples in the table, each of these contained about 95 parts by weight of commercial ethylene glycol. Entry number (4) of Table I shows the corrosion when the sodium tetraborate alone is employed. Entries Nos. (5) and (6) show the marked improvement obtained by the addition of a silicate, especially with respect to aluminum, cast iron, solder, and steel. Entry No. (8) shows the effect of leaving out the silicate despite the inclusion of the other components. Entry No. (7) shows the results of including all three corrosion inhibitors in the formulation. With the exception of the improvement of the brass corrosion over entry No. 4), the sodil um mercaptobenzothiazole appears otherwise to be of no benefit. A comparison entries numbered (1) and (2) in Table II shows clearly the long-term benefits of including the sodium mercaptobenzothiazole in the formulation and the cooling system. In Table II, the corrosion in terms of weight loss are in the same units as Table I.

TABLE I.MODIFIED NATIONAL BUREAU OF STANDARDS SIMULATED ENGINE CORROSION TEST 168 HOURS Coupon Weight Loss in rug/sq. cm.

(Average of Above and Below Liquid Level) Anti-Freeze Formulation (in parts by weight) Alum- Oop- Brass 801- Steel Cast mum per der Iron 6. 71 0.20 0.15 2.1 2. 2 8. 6 32. 8 0. 15 0. 0O 1. 24 5. 5 15. 4 18. 6 0.07 0. O7 0. 44 0. 11 2. 5 11.7 0.07 0.22 0. 91 0.80 8. 3 0.3 0.15 0.09 0. 24 0.1 0.11 0.18 0. 05 0.07 0.17 0.05 0.12 0.42 0. 05 O. 03 0.19 0.05 0.1 5. 45 0. O0 0. 00 0. 88 0. 15 O. 14

TABLE IL-MODIFIED NATIONAL BUREAU OF STAND- ARDS SIMULATED ENGINE CORROSION TEST 672 HO URS Alum- Copper Brass Solder Steel Cast inum Iron i3rnncl A 10. 41 0. 26 O. 15 1. O3 2. 45 17. 14 I 4. 23 0. 46 0. 25 1. 5 0.34 4. 63

See footnotes at bottom of Table I.

It should be pointed out at this time that sodium silicate (40 B. water glass) is satisfactory and, with respect to corrosion inhibition, is almost as good as the sodium metasilicate in the composition. However, the sodium silicate when used in the anti-freezes of this invention is prone to leave soft, white deposits on the radiator cores of cooling systems, and the anti-freeze compositions are unstable when mixed with hard water. Hence, the two silicates are not to be regarded as equivalents.

The blending technique or method which has been found advantageous is as follows: The borax is first dissolved in a water-glycol blend to form a premix concentrate. The silicate is first dissolved in water. The borax, water-glycol concentrate blend is mixed with additional glycol to obtain the approximate desired borate concentr-ation. The aqueous silicate solution is then metered into the dilute borate water-glycol solution in a small stream with good and vigorous agitation throughout the addition and for a period thereafter. The above-described blending technique will greatly facilitate rapid solution and avoid the precipitation of silica from the formulation. Of course, any other components added, such as the sodium mercaptobenzothiazole, may be added directly to the glycol and at any time. Heat can be used if desired to facilitate dissolution of any components above. Usually a temperature of to F. sufiices for rapid dissolution.

Naturally standard components added for commercial appeal such as dyes may be added if desired to the formulations of this invention. The amount of dyes in such a case being small in all cases, often much less than 0.01.

If a dye is employed a lesser amount of some other component in its operative range will have to be employed, as may be possible in the case of other components because of the volume limitation sometimes placed on the formulation by standard packaging. The various dyes and quantities of each are subject to wide variation, and such is well known in the art, having heretofore become widely use-d and practiced.

While the anti-freeze formulations discussed hereinabove are quite satisfactory, I have found a yet superior and non-equivalent embodiment of the invention.

The particular embodiment to be subsequently described has the advantages of requiring smaller quantities of the borate additive or slightly better corrosion inhibition and more important provides for concentrates which are less corrosive and still more important prov-ides concentrates which exhibit improved storage stability.

This is accomplished by employing a mixture of sodium metaborate and sodium tetrabo-rate instead of sodium tet-raborate alone in the formulation. The best manner of obtaining this mixture is to form it in situ by the addition of sodium hydroxide to either a sodium tetraborate or to the formulation which contains the sodium tetraborate. It will be found more convenient in determining the caustic to be added to regulate it on a pH basis. The pH in any case should be above about 6.5 and preferably is above about 7. When the pH drops below about 6.5, the anti-freeze formulation experiences storage difficulties. Although the pH should be above about 7, the pH should never be above about 11 and preferably is about 7.5 to 8.5.

In connection with the caustic addition, a 50 percent aqueous solution is preferred in practice. This is because it has been found advantageous in handling, blending, and in achieving economies.

It is to be understood that the presence of the metaborate form exclusively for the borate of this invention is not equivalent to the mixture of borates in the finished concentrate. This is true whether the metaborate is formed in situ or is employed initially in that form. The reasons for this are that, when only the metaborate is present in the concentrate, a pH higher than that for best corrosion protection is obtained. When the tetraborate exclusively is employed, the pH is below about 6.5, where, as mentioned, the concentrate will experience storage difliculties. Thus it can be seen that a mixture of sodium tetraborate and sodium metaborate in the formulation is unexpectedly superior than either employed alone.

In the case of the mixture of the two forms of borate in the formulation, the quantities of materials involved are as follows:

Broad Preferred Sodium borate mixture (here being About 1.0 to About 1.50 to the sodium tetraborate pentahyabout 3.5. about 3.0. drate and sodium metaborate octahydrate forms). Sodium metasilicate pentahydrate... About 0.01 to About 0.1 to about 0.3. about 0.25. Sodium mercaptobenzothiazole. About 0005 to About 0.01 to about 0.5. about 0.3. Ethylene glycol (containing other About 95.

glycols).

amounts of the other borate forms would be used to obtain the concentrations shown in the table above.

In the formulations demonstrated in the above table, there must be a minimum of about 0.9 part water when about 0.3 part sodium silicate is employed. Otherwise water is simply added as make-up to obtain a total of parts. Thus in the particular formulation where the sodium silicate is employed in about 0.3 part, the bo-rate cannot be 3.5 parts and must be reduced. As a general rule, the minimum of water that is to be employed is three times as much by weight of the sodium meta-silicate so that the silicate will be kept in solution. In calculating the water requirements in the total formulation, one must include the water from all sources such as the water of hydration, if any, and not just free water.

The following compositions are illustrative formulations contemplated in this embodiment and which have actually been tested and found highly effective formula tions. Each formulation contained, in addition to that shown in the table the following compounds and in the parts shown: 0.2 sodium metasilicate, 0.02 sodium mercaptobenzothiazo le (added as a 50 percent aqueous solution), 95.5 commercial ethylene glycol and 0.0065 dye.

Borax NaOH Ratio. Total (pentahy- (anhy- H O metal Borates drate) drous) tetra An antiseep agent such as but not limited to the phosphorus compounds may also be added to this embodiment.

Blending in this latter embodiment will be the same as with the preceding embodiments. The caustic can be added at any time; however we prefer to add it to the borate in the beginning.

It is to be understood that the above description is given by way of illustration and that deviations are possible within the spirit of the invention which are to be construed as within the purview of the appended claims.

The invention having thus been described, what is claimed and desired to be secured by Letters Patent is:

1. A corrosion inhibited single-phase anti-freeze formulation comprising a water miscible glycol containing a corrosion inhibiting amount of a corrosion inhibitor system on a weight basis consisting of the following two ingredients, sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetraborate pentahydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, and additionally about 1.0 to about 5.0 parts of water with the further provision that said amount of water is at least three times as much as said sodium metasilicate employed in the inhibitor system.

2. A corrosion inhibited single-phase anti-freeze formulation comprising a glycol containing a corrosion inhibiting amount of 'a water miscible corrosion inhibitor system on a weight basis consisting of the following three ingredients, sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetrabor-ate pentahydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, and additionally about 1.0 to about 5.0 parts of water with the further provision that said amount of water is at least three times as much as said sodium metasilicate employed in the inhibitor system.

3. A corrosion inhibiting additive composition for use in Water miscible glycolic au-ti freeze formulations on a weight basis consisting of sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetraborate pentahydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium meta- 7 silicate pentahydrate, and about 0.005 to about 0.5 part of mercaptobenzothiazole.

4. A corrosion inhibiting additive composition for use in water miscible glycolic anti-freeze formulations on a Weight basis consisting of sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetraborate pentahyd-rate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, and about 1.0 to about 5.0 parts of water.

5. An additive composition for use in water miscible glycolic anti-freeze formulations on a weight basis consisting of sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetraborate pent-ahydrate, sOdium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilic-ate pentahydra-te, about 1.0 to about 5.0 parts of water, about 0.005 to about 0.5 part of sodium mercaptobenzothi-azole, and about 0.01 to about 2.0 parts of tributoxyethylphosphate.

6. An inhibited single-phase anti-fireeze formulation which comprises on a weight basis about 89.20 to about 96.985 parts of a water miscible glycol and about 3.015 to about 1080 parts of an additive composition as the only corrosion inhibitors consisting of on a weight basis a sodium borate in an amount equivalent to about 2.0 to about 3.0 parts of sodium tetraborate pentahydrate, a sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium mebasilicate pentahydrate, about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, and at least about 3 times as many parts of water, including water of hydration, as the silicate.

7. The formulation of claim 6 wherein the glycol is ethylene glycol.

8. An inhibited single-phase anti-freeze formulation which on a weight basis comprises about 95 parts ethylene glycol anda corrosion inhibitor system consisting of sodium borate, sodium metasilicate and sodium mercaptobenzothiazole, said corrosion inhibitor system is further defined as a sodium tetraborate equivalent in amount to about 2.5 to 2.75 parts of sodium tetr-aborate pentahydrate, a sodium metasilicate equivalent in amount to about 0.20 to about 0.3 part of sodium metasilicate pentahydrate, about 0.01 to about 0.5 part sodium mercaptobenzothiazole, and at least about three times as many parts of water, including water of hydration, as the silicate employed in the corrosion inhibitor system.

9. The method of preparing an inhibited single-phase anti-freeze formulation which comprises, dissolving about 2 to about 3 parts of sodium borate, in a water and water miscible glycol mixture to form a premix, adding addi tional glycol to the premix until a total of about 95 parts of glycol is obtained, separately dissolving sodium meta-silicate in water, said sodium metasilicate being dissolved being Ian amount equivalent to about 0.01 to 0.3 part of sodium metasilicate pentahydrate, adding said silicate solution to said borate premix slowly and simultaneously with vigorous agitation, adding about 0.005 to about 0.5 part of sodium mercaptobenzothiazole during the above process sequence, said parts in each case being based on weight, said formulation having a total water content including water of hydration of at least three times by weight relative to said silicate.

10. The method of preparing an inhibited single-phase antifreeze formulation which comprises, dissolving about 1.0 to about 3.5 parts of sodium borate wherein part of said borate is a mixture of sodium tetraborate and sodium metaborate in a water and water miscible glycol mixture to form a premix, then adding glycol to provide a total of about 95 parts of glycol, separately dissolving sodium metasilicate in water to form a sodium metasilicate solution, said sodium meta-silicate dissolved being an amount equivalent to about 0.01 to 0.3 part of sodium metasilicate pentahydrate, adding said silicate solution to said borate premix solution slowly and simultaneously agitating vigorously, adding about 0.005 to about 0.5 part of sodium mercaptobenZot-hiazole during the above process sequence, said formulation having a total of Water, including water of hydration, in the above formulation of at least three times by weight as said silicate.

11. The method according to claim 10 wherein said metaborate is formed in situ from said sodium borate by adding sodium hydroxide to said sodium borate which is in the form of sodium tetraborate to provide a formulation having a pH in the range above about 6.5 to and less than about 11.0.

v12. The method according to claim 11 wherein the pH is about 7.5 to about 8.5.

13. An inhibited single-phase anti-freeze composition which comprises on a weight basis a corrosion inhibitor system consisting of sodium borate, sodium metasilicate, and sodium mercalpto'benzothiazole, said corrosion inhibitor system being further defined as about 1.0 to about 3.5 parts of a mixture of sodium borates, about to about percent by weight of said sodium borate mixture being sodium metaborate and about 30 to about 10 percent being sodium tetraborate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part sodium metasilicate 'penta'hydrate, about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, about parts of ethylene glycol, :and at least about three times as many parts by weight of water, including water of hydration, as of the sodium silicate employed in the above inhibitor systom.

14. The method of preparing an anti-freeze formulation according to claim '10 wherein the ratio of said sodium met-aborate to said tetrabonate employed is such to provide a formulation having a pH above about 6.5 and less than about 11.0.

15. A method of preparing an anti-freeze formulation according to claim 11 wherein said menaborate is formed in situ from said tetraborate by adding sodium hydroxide to said sodium tetraborate to provide a formulation having a .pH in the range of about 7.5 to about 8.5 and wherein about 0.01 to about 2.0 parts of an anti-seep agent tributoxyethylphosphate is added.

16. The method according to claim 11 wherein said sodium mercapto'benzothiazole is formed in situ by adding mencaptobenzothiazole whereby said sodium hydroxide reacts with same to produce sodium mercaptobenzothiazole.

17. A corrosion inhibited single-phase anti-freeze formulation comprising on :a weight basis, about 91.70 to about 96.99 parts ofla water miscible glycol, a corrosion inhibitor system consisting of the following two ingredients, sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetr'aborate pentah-ydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, and additionally about 1.0 to about 5.0 parts of water with the further provision that said amount of water is at least 3 times as much as said sodium metasilicate employed in the inhibitor system.

18. A corrosion inhibited single-phase anti-freeze formulation comprising on a weight basis, about 91.20 to about 96.985 parts of a water miscible glycol, a corrosion inhibitor system consisting of the following three ingredients, sodium borate in an amount equivalent to about 2 to about 3 par-ts of sodium tetsabor-ate pentahydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, and additionally about 1.0 to about 5.0 parts of water with the further provision that said amount of water is at least 3 times as much as said sodium metasilicate employed in the inhibitor system.

19. An inhibited single-phase anti-freeze formulation comprising on a weight basis, about 89.20 to about 96.975 parts of a water miscible glycol, a corrosion inhibitor system consisting of the following three ingredients, sodium borate in an amount equivalent to about 2 to about 3 parts of sodium tetraborate pentahydrate, sodium metasilicate in an amount equivalent to about 0.01 to about 0.3 part of sodium metasilicate pentahydrate, and about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, about 1.0 to about 5.0 parts of water with the further provision that said amount of water is at least 3 times as much as said sodium metasilicate employed in the corrosion inhibitor system, and additionally about 0.01 to about 2.0 parts of tributoxyethylphosphate as an anti-seep agent.

20. An inhibited single-phase anti-freeze formulation comprising on a weight basis, about 95% ethylene glycol and about 5% of an additive composition comprising a corrosion inhibitor system consisting of the relative amounts of the following three ingredients, a sodium borate equivalent in amount to about 2.0 to about 3.0 parts of sodium tetraborate pentahydrate, a sodium metasilicate equivalent in amount to about 0.01 to about 0.3 part of sodium metasilic-ate pentahydrate and about 0.005 to about 0.5 part of sodium mercaptobenzothiazole, and as the remaining parts of the additive composition the relative amounts of the following two ingredients, about 0.01 to about 2.0 parts of tributoxyethyl phosphate as an anti-seep agent, and at least about 3 times as much water including a hydration \as the sodium met-asilicate employed in the conrosion inhibitor system.

21. An inhibitor single-phase anti-freeze formulation comprising on a weight basis, about 95 parts of ethylene glycol, a corrosion inhibitor system consisting of the following three ingredients, a sodium tetraborate equivalent in amount to about 2.5 to about 2.75 parts of sodium tetrabona-te pent-ahyd-rate, a sodium metasilicate equivalent in amount to about 0.20 to about 0.3 part of sodium metasilica-te pentahydrate, and about 0.01 to about 0.5 part of sodium mercaptobenzothiazole, as an anti-seep agent about 0.05 to about 0.15 part of tributox'yethyl phosphate, and additionally at least about 3 times as much water including water of hydration as the sodium metasilicate employed in the corrosion inhibitor system.

22. A corrosion inhibited single-phase anti freeze composition comprising on a weight basis, about 95 parts of ethylene glycol, and as a corrosion inhibitor system a sodium borate, a sodium metasilicate and sodium mercaptobenzothiazole said inhibitor system further characterized as about 1.0 to about 3.5 parts of sodium borate wherein said borate is a mixture of to 100 percent sodium metaborate and the remaining borate is 50 percent sodium .te-tarborate, about 0.01 to about 03 part of sodium metasilicate, about 0.005 to about 0.5 part of sodium mercapto'benzothiazole, and additionally sufficient water to provide for a total of 100 parts in the composition with the further provision that there is at least 3 times as much water as said sodium metasilicate employed in the inhibitor system.

23. An anti-freeze formulation according to claim 22 wherein the ratio of sodium metaborate to te-traborate is such to provide a formulation having a pH between about 7.5 and 8.5.

24. A corrosion inhibited single-phase anti-freeze composition comprising on a Weight basis, about 95 parts of ethylene glycol, and as a corrosion inhibitor system a sodium borate, a sodium metasilicate and sodium mercapto b'enzothiazole, said inhibitor system further characterized as about 1.5 to about 3.0 parts of sodium borate wherein said sodium borate is a mixture of about to about 90 percent of sodium metabor-ate and the remaining borate is about 30 to about 10 percent of sodium tetraborate, sodium metasilicate in an amount equivalent to about 0.1 to about 0.25 part sodium metasilicate pentahydrate, about 0.01 to about 0.3 part sodium mercapto-benzothiazole, and additionally a minimum of about 3 times as much water including water of hydration as the sodium metasilicate employed in the inhibitor system.

References Cited by the Examiner UNITED STATES PATENTS 2,373,570 4/ 1945 Keller 25|275 2,815,328 12/ 1957 Green et a1 252- 2,961,291 11/1960 Pickett et .al. 252-74 X 2,972,581 2/1961 Johnson et a1 25275 3,042,620 7/1962 Dry et al 25275 X LEON D. ROSDOL, Primary Examiner.

JULIUS GREENWALD, Examiner.

J. D. WELSH, Assistant Examiner. 

1. A CORROSION INHIBITED SINGLE-PHASE ANTI-FREEZE FORMULATION COMPRISING A WATER MISCIBLE GLYCOL CONTAINING A CORROSION INHIBITING AMOUNT OF A CORROSION INHIBITOR SYSTEM ON A WEIGHT BASIS CONSISTING OF THE FOLLOWING TWO INGREDIENTS, SODIUM BORATE IN AN AMOUNT EQUIVALENT TO ABOUT 2 TO ABOUT 3 PARTS OF SODIUM TETRABORATE PENTAHYDRATE, SODIUM METASILICATE IN AN AMOUNT EQUIVALENT TO ABOUT 0.01 TO ABOUT 0.3 PART OF SODIUM METASILICATE PENTAHYDRATE, AND ADDITIONALLY ABOUT 1.0 TO ABOUT 5.0 PARTS OF WATER WITH THE FURTHER PROVISION THAT SAID AMOUNT OF WATER IS AT LEAST THREE TIMES AS MUCH AS SAID SODIUM METASILICATE EMPLOYED IN THEINHIBITOR SYSTEM.
 5. AN ADDITIVE COMPOSITION FOR USE IN WATER MISCIBLE GLYCOLIC ANTI-FREEZE FORMULATIONS ON A WEIGHT BASIS CONSISTING OF SODIUM BORATE IN AN AMOUNT EQUIVALENT TO ABOUT 2 TO ABOUT 3 PARTS OF SODIUM TETRABORATE PENTAHYDRATE, SODIUM METASILICATE IN AN AMOUNT EQUIVALENT TO ABOUT 0.01 TO ABOUT 0.3 PART OF SODIUM METASILICATE PENTAHYDRATE, ABOUT 1.0 TO ABOUT 5.0 PARTS OF WATER, ABOUT 0.005 TO ABOUT 0.5 PART OF SODIUM MERCAPTOBENZOTHIAZOLE, AND ABOUT 0.01 TO ABOUT 2.0 PARTS OF TRIBUTOXYETHYLPHOSPHATE. 